
//图片按比例缩放
var flag=false;
function DrawImage(ImgD,iwidth,iheight){
//参数(图片,允许的宽度,允许的高度)
var image=new Image();
image.src=ImgD.src;
if(image.width>0 && image.height>0){
   flag=true;
   if(image.width/image.height>= iwidth/iheight){
      if(image.width>iwidth){ 
         ImgD.width=iwidth;
         ImgD.height=(image.height*iwidth)/image.width;
     }else{
        ImgD.width=image.width; 
        ImgD.height=image.height;
     }
     ImgD.alt=image.width+"×"+image.height;
  }
  else{
     if(image.height>iheight){ 
         ImgD.height=iheight;
          ImgD.width=(image.width*iheight)/image.height; 
     }else{
        ImgD.width=image.width; 
        ImgD.height=image.height;
    }
    ImgD.alt=image.width+"×"+image.height;
   }
  }
} 
